In response the responses to my letter on 16th March (Job ads are not racist) I would like to say that my original letter was regarding whether or not it's okay to put 'native speakers only' need apply. Now, whether or not native speaker is used to mean we do not want black or Asian teachers is another story.
Yes, I know and every one else with experience here knows that schools do not generally want Asian or black teachers. This is because the students will feel like they've been lied to by the school when they were told that a NES would be teaching them. From a business stand point, you give your customers what they want. What the students want is a handsome white man or woman to teach them. No, I think that's unjust, but I also feel it's very unjust that Hooters won't hire me as a waiter. For those of you who don't know, Hooters is a large restaurant chain in America with attractive young females with large chests. Men like to eat there, and drink beer, and chat with the waitresses. I personally find it very sexist that they won't give me a job based solely on the fact that I'm not a young sexy female.
If you really want to get to the core of the issue, it's a religious one. But for those who live in the world today, you just have to accept the fact that businesses hire the people that their customers want them to hire. If you don't like it, then go to another company or country where things are just. For example, in America, no company would dare to ask for a photo with your resume. That would be begging for a lawsuit. So it would be just as silly for Hooters to put in their job advert that all are welcome to apply, as it would be for a Thai school to say the same thing.